For the patients or elders with mobility difficulties, as walking by themselves has been a big problem, these people have to sit or lie down for hours every day. This is not a good sign for patients' recovery. In addition, long-time sitting and lying may accelerate the degeneration of the body functions, as well as impose the burden put on the nurses. In order to enable the patients or elders having mobility difficulties to walk by themselves, consequently to help them heal quickly, prevent from body function degeneration, and defer senescence, a walking aid is invented to assist the patients or elders who have mobility difficulties to walk or stand for rest. With the walking aid, the patients or elders could walk or stand for rest against the walking aid independently. However, the conventional walking aids have not provide with the convenience in height self-adjustment thus the users have to bent to adjust the heights of the stands one by one by hand; and those walking aids cannot guarantee the consistence in heights of the stands, in particular, those walking aids can't assist the patients or elders to walk up or down the stairs.